In Cobbs v. Grant, 8 Cal. 3d 229 (1972), the California Supreme Court held that a physician’s duty to inform a patient before treatment is measured by what a reasonable patient would want to know, not by what other doctors in the community customarily disclose. The decision rejected the long-standing physician-based standard, grounded the new rule in the patient’s right of self-determination, and set out concrete disclosure obligations, three narrow exceptions, and an objective test for causation. It remains the foundational informed consent authority in California and has been adopted in some form by roughly half of U.S. states.
What the Court Decided
The core holding is a shift in whose judgment controls the conversation before treatment. Under the older rule, a doctor’s disclosure duty was defined by local medical custom, and proving a breach required expert testimony from other physicians about what they would have said. The court found this circular: it let the profession decide how much patients deserved to know.
In its place, the court adopted a patient-based standard. The scope of a physician’s disclosure must be measured by the patient’s need, and that need is whatever information is material to the decision a reasonable person in the patient’s position would make. The right to decide what happens to your own body, the court reasoned, means little without the information required to exercise it intelligently.
The practical difference is significant. A doctor can no longer stay silent about a serious risk simply because other local physicians also stay silent. The question is whether a reasonable patient would have wanted to know.
What a Physician Must Disclose
The patient-based standard translates into specific obligations before any non-emergency procedure.
When a procedure carries a known risk of death or serious bodily harm, the physician must disclose that risk and explain the potential complications in language the patient can understand. This duty applies even when the probability of the complication is low, because the severity of the possible outcome is what makes it material.
The duty extends beyond the proposed treatment itself. A physician must reasonably disclose the available alternatives and the dangers of each, including non-surgical options, different surgical approaches, and the option of doing nothing. A patient who hears only about the recommended procedure cannot make a genuinely informed choice.
The expected benefits and the likelihood of success belong in the same conversation. Weighing a surgery with a 90% success rate is a different decision than weighing one with a 50% chance of working. The physician is not expected to deliver a medical school lecture, but the discussion must give the patient enough to weigh the realistic tradeoffs.
The Three Exceptions
The court recognized that a rigid disclosure rule would be unworkable in every situation and carved out three narrow exceptions.
Emergency
When a patient is unconscious or otherwise unable to consent and faces an immediate threat to life or health, the physician may proceed without disclosure. The patient’s interest in survival outweighs the interest in informed decision-making when no conversation is possible.
Patient Waiver
A patient can choose not to be informed. If a patient tells the doctor they would rather defer entirely to medical judgment and not hear the risks, the physician is not required to force the information on them. The right of self-determination includes the right to delegate the decision.
Therapeutic Privilege
The most contested exception allows a physician to limit disclosure when the information itself would seriously harm the patient. The court described this narrowly: situations in which full disclosure would have so seriously upset the patient that the patient could not have rationally weighed the risks of refusing treatment. The physician bears the burden of proving, by a preponderance of the evidence, that the disclosure itself posed a genuine threat to the patient’s wellbeing. The exception cannot become a blanket justification for withholding bad news because the doctor expects the patient to be upset.
Battery or Negligence?
The court also settled a threshold question that had divided earlier cases: whether a disclosure failure is a battery claim or a negligence claim. The distinction matters for proof requirements and damages.
Battery applies when a doctor performs a procedure the patient never agreed to, or performs a substantially different procedure than the one authorized. Consent to surgery on the right knee followed by surgery on the left is battery, because the doctor deliberately deviated from the consent given.
Informed consent cases are different. When the patient agrees to a specific procedure and the doctor performs exactly that procedure, but an undisclosed risk later materializes, there was no intentional deviation from consent. The failure was in the quality of the information provided, and that failure sounds in negligence. The question becomes whether the physician met the duty of care in obtaining consent.
Proving the Claim: Objective Causation
Showing that a doctor failed to disclose a material risk is only half the case. The patient also has to prove causation: that the undisclosed information would have changed the decision, so the harm would not have occurred.
The court recognized a built-in problem with letting patients testify about what they would have done. After a complication has materialized, almost any patient will say they would have refused the procedure had they known. Hindsight makes that claim easy to assert and nearly impossible to disprove.
To address this, the court adopted an objective causation test. The question is not what this particular patient now claims they would have decided, but what a reasonably prudent person in the patient’s position, fully informed of the significant risks, would have decided. The patient can testify about their own reasoning, but that testimony alone is not dispositive.
This test is one of the most practical pieces of the ruling. It keeps informed consent claims from becoming automatic winners whenever a known risk occurs, while still protecting patients whose doctors left them genuinely uninformed about dangers that would have changed a reasonable person’s mind.
Why the Case Still Matters
Cobbs was decided the same year as the D.C. Circuit’s Canterbury v. Spence, and together the two rulings launched a nationwide move toward patient-based disclosure. About half of U.S. states now follow some version of the reasonable-patient standard; the rest continue to measure disclosure against medical custom.
In California, Cobbs remains the foundational authority on informed consent. State regulations governing healthcare facilities reference the decision directly, and California courts still apply its framework when evaluating whether a physician’s disclosure was adequate. The focus the court articulated in 1972, on what a reasonable patient needs to know rather than what the profession is comfortable sharing, continues to define the standard a doctor must meet before treatment.